Home wireless networks or PANs (Personal Area Networks) are designed to interconnect digital communications devices, for example telephones, personal digital assistants, speakers, television units, multimedia players, telephones, personal digital assistants, etc. situated in proximity to the user. The range of such a communications network is of the order of a few meters.
These networks can be wired (USB, Ethernet, Firewire) but can also rely on the use of a wireless medium. The term used for such a network is “wireless personal area network” or WPAN. The Bluetooth standards (IEEE 802.15.1), UWB, ZigBee (IEEE 802.15.4), IEEE 802.11 or IEEE 802.15.3 are presently the ones most used for this type of network.
Each of these standards proposes its own protocol of access to the physical data transmission layer, for example in order to share the use of a radio band between several apparatuses relative to specific applications needs. Certain of these protocols generally use a time division multiple access (TDMA) mode, which is a multiplexing mode for transmitting several signals on a single channel, that is particularly efficient for managing guaranteed bit rates with high synchronization constraints. This is a time multiplexing mode, the principle of which is that of subdividing the available time between the different connections. By this means, a same carrier frequency can be used by several devices.
Such wireless home networks use varied transmission frequencies ranging from 2.5 GHz to 60 GHz, the latter frequencies being particularly well-suited to transmitting data at very high bit rates over a limited range, for example as a means of connectivity between the different elements of a home cinema. Indeed, for this case of use, the range is limited to about ten meters (sufficient to cover the layout of this type of system in a room) and the bit rates brought into play are very high, beyond one gigabit per second, by the audio as well as video nature, as well as the very high resolution of the information transmitted.
Such wireless systems, although advantageous from the viewpoint of their installation, nevertheless have high sensitivity to interference and masking or shadowing phenomena.
It is therefore interesting to provide this type of system with a method for re-configuring the network (modifying the use of the bandwidth, adding or removing new devices) to overcome the above-mentioned problems of shadowing and ensure the synchronism of use of any new configuration. This configuration will then be able to work transparently, i.e. without perceptibly modifying the function of the system in use, especially by avoiding transmission at an inappropriate time (therefore a send operation that is disturbing) of a node of the network that is unable to receive a TDMA type access sequence information.
Many prior-art solutions propose to process the absence of information of a TDMA type access sequence when a node is unable to receive it through the master node of the network.
For example, the patent document US20080019347 describes a method enabling a node of the network to retrieve descriptive information on the current TDMA type access sequence. The patent document describes a system in which a master node, at each transmission cycle, announces the transmission sequence (or TDMA type access sequence) applicable for the duration of the cycle. A node unable to receive this information therefore loses the use of its time space (or slot) in the cycle. The patent document then proposes to define a period of the transmission cycle during which the node having detected poor reception or an absence of reception of TDMA type access sequence information (during a period known as a “beacon” period) will request another node of the system to re-transmit information characterising this TDMA type access sequence.
One drawback of this approach is that it cannot be used to ensure that the node will receive a TDMA type access sequence information if it is not linked with at least one node which itself has received information from the master node in the current cycle. This node has a very limited available time of resistance to shadowing (one transmission cycle) and does not ensure synchronization during the modification of the TDMA type access sequence.
The patent document U.S. Pat. No. 7,460,503 describes a “beacon” re-transmission technique (capable of containing a representation of the TDMA type access sequence) in which a “slave” node of a PNC (piconet coordinator) node or master node which, during a predefined time slot in the transmission cycle, re-sends the information of the beacon as received from the PNC. This makes it possible either for a node that cannot receive the PNC to know of the existence of the piconet (network) and hence to locate the existence of a network or provides for the most efficient possible co-existence when another neighboring piconet is set up (without any need for preliminary coordination). This technique may also enables a masked or shadowed node of the PNC to remain synchronized with it. One drawback of this approach is that it does not enable synchronization during temporary shadowing between the relay node and the PNC because this relay node acts only when it is capable of receiving information from the PNC.